The present invention relates generally to an optical fiber for use with a laser device and, more particularly, to an optical fiber having an improved diffuser configuration at its distal end for performing the dual functions of scattering light and providing a temperature signal.
Currently, surgeons employ medical instruments which incorporate laser technology in the treatment of benign prostatic hyperplasia, also commonly referred to as BPH. BPH is a condition of an enlarged prostate gland, where such gland having BPH typically increases in size by about two to four times. The laser energy employed by the surgeons to treat this condition is delivered by an optical fiber which must be able to distribute light radially in a predictable and controlled manner. During the course of such treatments, one parameter of great importance is the temperature of the tissue being treated. For example, one current recommendation for forming lesions in the prostate as a treatment for BPH is to heat a small volume of tissue to 85° C. for a designated time period depending on fiber and laser design. It will be appreciated that heating the tissue to a lesser temperature has the effect of incomplete lesion formation, while heating the tissue to a higher temperature can cause excessive tissue damage. Accordingly, the ability to accurately measure the temperature of the optical fiber tip during treatment is of primary concern.
It will be understood that there are several known ways of performing the temperature monitoring function for a laser system. One approach has been utilized in laser treatment systems known as the “Indigo 830e Laseroptic Treatment System” and the “Indigo Optima Laseroptic Treatment System,” both of which are manufactured by Ethicon EndoSurgery, Inc. of Cincinnati, Ohio, the assignee of the present invention. Methods of providing an optical fiber with a diffuser end are disclosed in U.S. Pat. No. 6,522,806 to James, IV et al., U.S. Pat. No. 6,361,530 to Mersch, and U.S. Pat. No. 5,946,441 to Esch. Each of these methods utilize the principle of relying upon the temperature dependence of the fluorescent response of a slug of material at the fiber tip to an optical stimulus as described in U.S. Pat. Nos. 5,004,913 and 4,708,494 to Kleinerman. More specifically, a pulse of pump energy causes a fluorescence pulse in an alexandrite slug which is delayed by a time interval corresponding to a temperature of the material.
It will be appreciated from each of the aforementioned patents that the slug is composed of a cured mixture of alexandrite particles and an optical adhesive which is cured in place. The current manufacture and assembly of such slugs is considered both complex and tedious. In an exemplary process, the slugs are formed in batches by sprinkling ground alexandrite into several tiny cavities in a mold placed on a vibratory plate. The alexandrite particles are then covered with an optical coupling adhesive, after which a vacuum is drawn and the mixture is cured within the mold using either heat or ultraviolet light. The slugs are removed from the mold as a batch and placed individually into the distal sleeve tip against the end of the fiber optic glass during assembly.
While various improvements have been made in the basic slug manufacturing process, they are all based on the slug being a mixture of alexandrite and adhesive and therefore have similar disadvantages. One disadvantage is that a portion of the final molded configuration is used as structural support, which results in substantial waste of the expensive alexandrite material. The manufacturing process is considered to be lengthy and requires the use of specialized equipment and highly trained operators. Moreover, the ratio of alexandrite to the ultraviolet binder (i.e., its concentration) in each individual cavity of the slug mold is not precisely controlled, which results in a variation of the slug composition and its resulting performance. It will also be understood that assembly of the slug within the distal tip of the optical fiber is difficult since the slug is unidirectional, the size of the components in the optical fiber is extremely small, direct visualization is not available, and neither mechanical positioning nor final mechanical interlock is provided between the components.
In an alternate variation of the current manufacturing process, an uncured mixture of alexandrite and adhesive may be directly applied to the end of the fiber and cured into place. This may be accomplished by dispensing the mixture within the tubing directly onto the end of the glass core, loading it into a sleeve or other carrier and seating the sleeve, or by dipping the core end into adhesive and then into the alexandrite particles. It has been found in this process, however, that application of a consistent amount of the mixture in the proper location is difficult to achieve and monitor on a production basis.
Thus, in light of the foregoing, it would be desirable for a slug, as well as a method of making and assembling such slug in an optical fiber, to be developed which overcomes the disadvantages associated with the alexandrite and adhesive composition and manufacturing processes described herein. It is also desirable that such slug would assist in centering the slug on the distal surface of the optical fiber and assuring contact between the fiber core and an outer sleeve, whereby the dual functions of light scattering and temperature sensing are optimized. Further, it is highly desirable for the light-scattering material and the sleeve of the diffuser portion for such optical fiber to be formed in an integral manner. In an alternative configuration, it would be desirable for the separate slug to be eliminated from the optical fiber and replaced with a tip diffuser having light scattering and temperature sensing capabilities which can be assembled to the distal end of the optical fiber.